Although the Place of Birth shows as Whitechapel, I wouldn't necessarily discount this on a census taken at somewhere like the Whitechapel Infirmary. My thinking is that it's unlikely the person completing the return went round every inmate getting accurate details and so probably made an educated guess in some cases. Shouldn't have done so obviously, but human nature being what it is...

Just a thought...I seem to recall people in need of the 'assistance' of the workhouse being sent back to their parish of origin. Given that it's almost certain Mary was...economical with the truth at the best of times, is it completely outrageous to think that she might have lied about her origins to secure a place in the workhouse most convenient for her?

I could be completely wrong, and I might be thinking of a time much earlier than Kelly.